Stoneflies are a primitive group of insects that’s been around for more than 300 million years. Stonefly naiads are aquatic and are found under rocks on rocky shores or clinging to rocks/gravel/branches/tree roots/debris/plants in the beds of flowing, well-oxygenated waters. In the far north, they are also found in cold lakes.
It’s a good thing that the BugLady doesn’t have nearby neighbors (or a Home Owners’ Association) who might be alarmed about someone who turns on the porch light and then creeps around taking pictures of porch critters at midnight.
Not a true fly, Stoneflies do have two sets of wings, which they tuck tightly across their body at rest. The naiads are aquatic and are found in flowing (well-aerated) water, where they live for up to three years. The nymphs are primitive-looking, flat and have strong claws. The larvae of some species of stoneflies are predators, and others feed on plant material that falls into the water.